It is proposed that an integrated ammonia-PEM fuel cell could unlock the potential of ammonia to act as a high capacity chemical hydrogen storage vector and enable renewable energy to be delivered eectively to road transport applications. Catalysts are developed for low temperature ammonia decomposition with activity from 450 K (ruthenium and cesium on graphitised carbon nanotubes). Results strongly suggest that the cesium is present on the surface and close proximity to ruthenium nanoparticles and that it produces activity in ruthenium by donation of electrons. The activity of sustainable cobalt for ammonia decomposition is shown to be a function of particle size and is more active on microporous carbon supports compared to mesoporous ones. Unlike ruthenium, activity for cobalt was not inuenced by the degree of surface graphitic nature and cobalt supported on microporous carbon approached the activity of ruthenium on the same support. In accordance with the sustainable objectives of this thesis, a case-study on the sustainability of ammonia as a sustainable hydrogen storage vector was undertaken. In this scheme, hydrogen produced from renewable electricity by electrolysis is con- verted to ammonia by the Haber-Bosch process and then converted back to deliver pure hydrogen at the point of use. The energy eciency and carbon footprint fell short of targets set by the US Department of Energy and the UK Department for Transport, the biggest impact was the production of hydrogen by electrolysis and not the Haber-Bosch process which accounts for only 9 % of total energy losses. To assess the feasibility of the ammonia-PEM fuel cell, a conceptual design was un- dertaken to quantify the palladium membrane size and catalyst quantity required for a typical road transport vehicle. The predicted quantity of palladium was excessive and future work must consider improvements to membrane technology.

Ever rising power densities and smaller transistor dimensions are increasing the challenge of thermal management within integrated-circuit chips and their surrounding packaging. In addition, the need for sustainable energy has placed urgent emphasis on energy conversion. Thermoelectric phenomena, involving the conversion of heat to electrical current, provide a central focus for both needs. Specifically, there is a need to engineer materials or composites with low thermal conductivity and high electrical conductivity for energy conversion and the opposite for heat management. In this presentation, experimental results will be presented of the specific heat and thermal conductivity of cobalt nanowires (CoNW), carbon nanotubes (CNT) and polymer-carbon nanotubes, in various composite arrangements with our high precession Calorimetric technique. Due to the nature of these samples, boundary and defect scattering of phonons in nanomaterials can dominate. This scattering phenomena shows decreasing thermal conductivity in metal nanowires, turns to be good for thermoelectric application. For the CNT, and possibly due to the high volume per atom leading to ballistic phonon propagation, the observed thermal conductivity along the nanotube direction, which leads to manage the heat dissipation problem in integrated circuits (ICs) and microprocessors. The thermal conductivity of a single Single-Wall Carbon Nanotube (SWCNT) was found to be 6600 W/mK, theoretically, twice that of diamond. When such high thermal conductivity materials are dispersed in a low thermal conducting polymer (PMMA), the effective thermal conductivity and thermal stability of the composite can change dramatically. The experimental results show good agreement with theoretical model proposed by Nelsen, Hamilton, Crosse, Geometric, and Xue. The thermal relaxation phenomena such as glass transition temperature (Tg) and dynamics of the molecules in the polymer-nanotubes composites, changes significantly different than the pure polymers during thermal treatment and is one of the focusing point of this presentation. Liquid crystalline materials confined to restrictive nano-channels are of great interest in many potential applications of electro-optics and display technology. This part of the presentation investigates the unexplored phenomenon of the coating and filling of 8CB and 10CB liquid crystals inside ~200nm diameter Multi-Wall Carbon nanopipes. The phase transition characteristics of the confined liquid crystal films were studied using MDSC technique and will be the last part of this presentation.

"Recently, nanomaterials have been vigorously studied for the development of biosensors. Among them, carbon nanotubes (CNTs) have stimulated enormous interest for constructing biosensors due to their unique physical and chemical properties such as high surface-to-volume ratio, high conductivity, high strength and chemical inertness. Our study is to develop a general design of biosensors based on vertically aligned CNT arrays. Glucose biosensor is selected as the model system to verify the design of biosensors. In the preliminary design, glucose oxidase (GOx) is attached to the walls of the porous alumina membrane by adsorption. Porous highly ordered anodized aluminum oxide (AAO) prepared by two-step anodization are used as templates. Deposited gold on both sides of template surfaces serve as a contact and prevent non-specific adhesion of GOx on the surface. In order to find out optimized thickness of gold coating, the oxidation and reduction (redox) reaction in [Fe(CN)6]3¨C /[Fe(CN)6]4¨C system is monitored by Cyclic Voltammetry (CV). Subsequently, enzymatic redox reaction in glucose solutions is also attempted by CV. We expect protein layers with GOx form a conductive network. However, no obvious enzymatic redox reaction is detected in the voltammogram. To take advantage of the attractive properties of CNTs, the design of enzyme electrodes is modified by attaching CNT onto the sidewalls of AAO template nanopores and then immobilizing GOx to the sidewalls and tips of CNTs. AAO templates provided vertical, parallel, well separated and evenly spacing nanochannels for CNT growth. Cobalt is used as a catalyst to fabricate CNTs. As a result, multi-walled carbon nanotubes (MWCNTs) are fabricated inside the AAO templates by catalytic chemical vapor deposition (CCVD). Characterization of AAO templates and cobalt electrochemical deposition are employed by scanning electron microscope (SEM), and energy dispersive X-ray spectrometry (EDS). Detailed structure and texture of CNTs are examined by transmission electron microscope (TEM). "

O presente trabalho teve por objetivo avaliar alterações devido à exposição a Nanotubos de Carbono de Parede Simples (NTCPS) em duas linhagens celulares epiteliais (BBnt e HK2) e em uma linhagem celular monocítica (THP-1), enfocando os mecanismos de internalização e os efeitos sobre o ciclo celular. Foi avaliada a ação dos receptores scavenger na internalização dos NTCPS nas células HK2 e THP-1 e a interferência de duas concentrações de NTCPS sobre os elementos do citoesqueleto e no ciclo celular, nas células HK2 e BBnt. As concentrações utilizadas foram equivalentes as permitidas pelo The National Institute for Occupational Safety and Health: 2,4 e 24 mg/cm2. A análise de expressão de mRNA por RT-PCR para receptores scavenger, mostrou que a internalização do NTCPS pode ocorre por endocitose. Sendo que os receptores SCARA5 e SRA são os responsáveis pela internalização nas células THP-1, enquanto MARCO e SRA realizam o processo de internalização nas células HK2. Observou-se que em ambas as concentrações, as células BBnt apresentaram amplificação centrossômica, com a ocorrência de 25,38% e 28,46% de mitoses alteradas para cada concentração, respectivamente. Não houve interferência significativa na progressão do ciclo celular em ambas as linhagens. O estudo da interação dos NTCPS com vesículas lipídicas não apresentou evidencias de alterações ou danos na membrana das vesículas, porém as vesículas apresentaram-se associadas umas às outras após o tratamento com 24 mg/cm2. / This study aimed to assess changes due to exposure to of Single-wall Carbon Nanotubes (SWCNT) in two epithelial cell lines (BBnt and HK2) and a monocytic cell line (THP-1), focusing on the mechanisms of internalization and effects on the cell cycle. The action of scavenger receptors in the internalization of SWNTC in HK2 and THP-1 cells and the interference of two concentrations of SWNTC about elements of the cytoskeleton and the cell cycle, in BBnt and HK2 cells was evaluated. The concentrations used were equivalent to those allowed by The National Institute for Occupational Safety and Health: 2,4 to 24 mg/cm2. Analysis of mRNA expression by RT-PCR for scavenger receptors showed that the SWNTC internalization can occurs by endocytosis. Being that SCARA5 and SRA receptors are responsible for internalization in THP-1 cells, while MARCO and SRA perform the process of internalization in HK2 cells. It was observed that at both concentrations, the cells showed centrosome amplification in BBnt cells, with the occurrence of 25.38% and 28.46% of mitosis changed for each concentration, respectively. There was no significant interference with cell cycle progression in both strains. The study of the interaction of lipid vesicles with SWNTC showed no evidence of change or damage the membrane of the vesicles, but the vesicles were associated with each other after treatment with 24 mg/cm2.

The crystalline iron-based nanowires encapsulated by multiwalled carbon nanotubes have been the subject of numerous studies owing to the range of potential applications. The presence of a-Fe (bcc)/y -Fe(fcc) junctions o ers the possibility of exploitation of the exchange bias effect, an interfacial magnetic phenomenon that plays a major role in magnetocaloric cooling, spintronic and high-density magnetic storage devices. This work is concerned with the synthesis and microstructural characterization of Fe-based and NiFe nanowires encapsulated by multiwall carbon nanotube radial structures. The known attributes of these structures are well matched to the magnetocaloric application. The primary aim of this work was to determine the unknown microstructural details of the encapsulated nanowire that are of relevance to the magnetocaloric application (junction types, location and orientation relative to the nanotube axis). The secondary aim was to explore the modi cation of the synthesis route to promote desirable attributes. This is the first report of a-Fe/y -Fe sequential junctions and a-Fe/Fe3C concentric junctions in encapsulated Fe-based nanowires. The presence of a-Fe/y -Fe junctions was inferred from the observation of a-Fe nanowires terminated by a ~100 nm length y-Fe crystallites of larger diameter. The a-Fe/Fe3C junctions exhibit the Bagaryatski orientation relationship: [110 ]bcck[100 ]orth. The degree of substrate roughness was found to be a means of tailoring details of the structure and composition of the encapsulated nanowires. NiFe encapsulated nanowires were found to contain crystallites of a-NiFe, y-NiFe and Ni3Fe and the sequential junctions -NiFe/Ni3Fe and a-NiFe/y-NiFe junctions.

Neste trabalho investigou-se a influência do cobre em diferentes catalisadores a base de níquel na decomposição catalítica do metano. Foram avaliados desde aspectos relacionados ao tratamento térmico das amostras até o desempenho catalítico nos testes de atividade. As amostras foram preparadas a partir de dois métodos diferentes. Um grupo foi preparado pelo método de impregnação úmida utilizando sílica como suporte, enquanto o segundo foi preparado pelo método de coprecipitação contínua, utilizando nitratos de cobre, níquel e alumínio em diferentes composições molares. Os ensaios foram realizados em reator tubular de leito fixo acoplado a um forno com controle de temperatura e conectado em linha com cromatógrafo gasoso. Utilizou-se 100 mg de amostra, numa faixa de temperatura de 500 a 750°C, utilizando como alimentação uma mistura reacional de N2:CH4 na proporção de 9:1. A caracterização das amostras foi realizada através das análises de SBET, TGA, TPR, TPO, DRX e Espectroscopia Raman. Os resultados mostraram uma significativa influência do cobre na atividade das amostras em temperaturas superiores a 500°C. A presença de cobre influenciou a área específica e a temperatura de redução das amostras calcinadas. Pequenas quantidades de cobre contribuem ao evitar a desativação do catalisador por sinterização em temperaturas superiores a 500°C. Para os catalisadores coprecipitados, além da influência do cobre, avaliou-se também a influência do gás utilizado no tratamento térmico das amostras. Foram utilizadas amostras não calcinadas, amostras calcinadas em ar por seis horas e calcinadas em N2 pelo mesmo período. Os resultados indicaram que a presença de cobre contribui para uma maior estabilidade e atividade nos ensaios realizados nas temperaturas de 600 e 650°C, principalmente para as amostras calcinadas em ar. As amostras com 11% de cobre na composição apresentaram elevada estabilidade na temperatura de 600°C, mesmo quando não calcinadas, indicando que a etapa de tratamento térmico pode ser evitada para este tipo de amostra. As análises de DRX, TPO e Espectroscopia Raman sugerem que o carbono formado, tanto para os catalisadores suportados quanto para os coprecipitados, depositou-se na forma de nanotubos de paredes múltiplas. / The effect of copper in different nickel-based catalysts in the catalytic decomposition of methane was investigated. Were evaluated aspects from the heat treatment of the samples to the catalytic performance in activity tests. Samples were prepared using two different methods. One group was prepared by the wet impregnation method using silica as the support and the second group was prepared by continuous coprecipitation method using copper nitrate, nickel and aluminum in different molar compositions. Catalytic activity runs were carried out in a tubular fixed-bed reactor coupled to an oven with temperature control and connected in line with a gas chromatograph. Samples of 100 mg were used in a temperature range of 500 to 750°C applying a reaction mixture of N2:CH4 at a ratio 9:1 as feed supply. The characterization of the samples was performed through the analysis of SBET, TGA, TPR, TPO, XRD and Raman spectroscopy. The results showed a significant effect of copper on the activity of the samples at temperatures above 500°C. The presence of copper influenced the specific area and the reduction temperature of the calcined samples. Small amounts of copper contributed to avoid catalyst deactivation by sintering at temperatures above 500°C. For the coprecipitated catalysts in addition to the influence of copper, the effect of the gas used for the thermal treatment of samples was also evaluated. Uncalcined samples and samples calcined in air and in N2 for six hours were used. The results indicated that the presence of copper contributed to a superior stability and activity in runs performed at temperatures of 600 to 650°C, especially for samples calcined in air. Samples with 11% of copper showed high stability at 600°C, even if not calcined, indicating that the thermal treatment step can be avoided for this type of sample. The XRD, TPO and Raman spectroscopy results suggest that the carbon deposited on the spent catalysts was in the form of multi-walled nanotubes, for both the supported and the coprecipitated catalysts.

Esta tese apresenta um estudo original das propriedades estruturais e eletrônicas dos nanotubos de carbono de parede simples (NTCPS) por meio de complexos de titânio e a possibilidade de adsorção e redução do cromo hexavalente Cr (VI) utilizando a teoria da densidade funcional. Cr (VI) é um dos principais poluentes ambientais, sua remoção apresenta várias dificuldades, e resulta em poluição ambiental, causando problemas de saúde. A adsorção de Cr (VI) foi investigada a partir das moléculas de cromato e dicromato no semicondutor NTCPS funcionalizado com complexos de TiO2, TiO4H4 e Ti2O6H4. Os resultados sugerem que os NTCPS funcionalizados são grandes candidatos à adsorção de Cr (VI). Além disso, as estruturas de banda eletrônica mudaram na região próxima à energia de Fermi das bandas de valência e de condução para os NTCPS pristino e funcionalizados com sistemas de cromo. Após adsorção de Cr (VI) nos sistemas, observa-se a formação de moléculas com menor toxicidade e atividade carcinogênica o que não ocorreu sem a presença dos nanotubos. / This thesis presents an original study of the structural and electronic properties of doped single-walled carbon nanotubes (SWCNT) through titanium complexes and the possibility of adsorption and reduction of hexavalent chromium Cr(VI) using density functional theory. Cr(VI) is one of the major environment pollutants, its removal presents several difficulties, and it results in industrial pollution, causing health problems. The adsorption of Cr(VI) was investigated from the chromate and dichromate molecules in semiconductor SWCNT functionalized with TiO2, TiO4H4 and Ti2O6H4 complexes. The results suggest that the functionalized SWCNT are great candidates to adsorb Cr(VI). In addition, the electronic band structures changed in the region near the Fermi energy of the valence and conduction bands for the pristine and functionalized SWCNT with chromium systems. After adsorption of Cr(VI) in the systems, the formation of molecules with less toxicity and carcinogenic activity is observed, which did not occur without the presence of the nanotubes.nanotubes.

Le sujet de cette thèse se situe dans le contexte de l'électronique organique à base de polymères conjugués et de nanotubes de carbone. Nous avons choisi la famille des polyfluorènes principalement en raison de leur émission dans le bleu, leur bon rendement quantique ainsi que pour la facilité avec laquelle on peut modifier leurs propriétés en greffant différents groupements fonctionnels sur la structure de base du fluorène. L'originalité des recherches effectuées au laboratoire concerne la structure des films électroluminescents que nous réalisons. Leur principe de fonctionnement repose sur l'utilisation de nanotubes de carbone en tant que film support pour le dépôt du polymère. Le travail réalisé au cours de cette thèse a principalement consisté à élaborer des films de polymères avec des épaisseurs et des taux de dopage contrôlés à la surface des nanotubes de carbone en optimisant les divers paramètres de synthèse électrochimique. Nous avons également utilisé des groupements fonctionnels pour améliorer les performances du polyfluorène et augmenter la compatibilité entre les couches polymère/nanotubes de carbone. Dans cette optique, nous avons mis en œuvre l'utilisation de différents outils pour la caractérisation des propriétés des films. Les propriétés intrinsèques des nanotubes de carbone ont donc pour effet de doper le polymère et d'améliorer le transport des charges au sein des couches tout en maintenant les performances de luminescence dans le bleu des polyfluorènes. / The subject of this thesis lies in the context of organic electronic based on conjugated polymers. We have chosen the class of polyfluorene mainly because of their blue emission, good quantum efficiency and possibility of modifying their properties by grafting side chain groups. The originality of our research relies upon the use of a particular devices structure. The structure of our electroluminescent films is based on the use of a thin layer of carbon nanotubes added to the structure of the emissive layer without involving any chemical modification.The work done in this thesis has mainly consisted of deposing polymer films with thicknesses and doping level controlled on the surface of carbon nanotubes by optimizing various parameters of the electrochemical synthesis. Functional groups have also been grafted on the side of chains in order to improve the performances of the polymer and to increase the compatibility between the polymer layer and the carbon nanotube dispersion. The use of carbon nanotubes should improve the charge carriers whitout quenching the photophysical properties of the polymers.

In this study, we designed a series of experiments to determine the factors governing ion permeation through individual carbon nanotubes (CNTs) less than 1.5 nm in diameter and 20 µm in length. We then rationalize the experimental results by using a model, which is drawn from previous literature on protein ion channels and is centered around a simplified version of the Gouy-Chapman theory of electrical double layer. Lastly, we experimentally demonstrate and discuss the general similarities in ion permeation characteristics between CNTs and biological ion-selective pores. The role of many potential factors influencing the ion transport is assessed by taking two experimental approaches: (1) studying the effect of electrolyte concentration and composition on channel conductance and reversal potential, and (2) examining a second type of nanochannel as a parallel ion conduction pathway within the same device architecture and measurement set-up, which we refer to as leakage devices. This helps to differentiate the effect of CNT on ionic transport from any other possible source. Taken together, these two experimental methods provide strong evidence that the electrostatic potential arising from ionized carboxyl groups at the nanopore entrance has a significant effect on ionic permeation in a manner consistent with a simple electrostatic mechanism.

Nano-materials are interesting material category with a single unit size between 1 and 1000 nanometers and possess unique mechanical, electrical, optical, and other physical properties that make them stand out from ordinary materials. With increasing demand for reduced size of electronic devices and integrated micro/nano-electro-mechanical systems (MEMS / NEMS), there is a high driving force in scientific research and technological advancement in nanotechnology. My research is about two popular novel nanomaterials: carbon nanotubes (1-dimensional material) and thin-layer transition metal dichalcogenides (2-dimensional materials). My first research direction is about the characterization of electrical properties of carbon nanotubes and using them as bio-sensors. Carbon nanotubes (CNTs), in general, are a material of great interest for many applications since their first discovery in 1991 [1], due to their unique structure, extraordinary electrical and mechanical properties, and unusual chemical properties. High-throughput fabrication of carbon nanotube field effect transistors (CNTFETs) with uniform properties has been a challenge since they were first fabricated in 1998. We invent a novel fabrication method to produce a 1×1 cm2 chip with over 700 CNTFETs fabricated around one single carbon nanotube. This large number of devices allows us to study the stability and uniformity of CNTFET properties. We grow flow-aligned CNTs on a SiO2/Si substrate by chemical vapor deposition and locate a single long CNT (as long as 1 cm) by scanning electron microscopy. Two photolithography steps are then used, first to pattern contacts and bonding pads, and next to define a mask to ‘burn’ away additional nanotubes by oxygen plasma etch. A fabrication yield of ~72% is achieved. The authors present statistics of the transport properties of these devices, which indicates that all the CNTFETs share the same threshold voltage, and similar on-state conductance. These devices are then used to measure DNA conductance by connecting DNA molecule of varying lengths to lithographically cut CNTFETs. While one single carbon nanotube is considered 1-dimensional material because it only has one side with “non-nano” length, the thin-layer transition metal dichalcogenides (TMDCs) are called the 2-dimensional materials since they have two sides of normal lengths and the other side of atomic size. Atomically thin materials such as graphene and semiconducting transition metal dichalcogenides have attracted extensive interests in recent years, motivating investigation into multiple properties. We use a refined version of the optothermal Raman technique [2][3] to measure the thermal transport properties of two TMDC materials, MoS2 and MoSe2, in single-layer (1L) and bi-layer (2L) forms. This new version incorporates two crucial improvements over previous implementations. First, we utilize more direct measurements of the optical absorption of the suspended samples under study and find values ~40% lower than previously assumed. Second, by comparing the response of fully supported and suspended samples using different laser spot sizes, we are able to independently measure the interfacial thermal conductance to the substrate and the lateral thermal conductivity of the supported and suspended materials. The approach is validated by examining the response of a suspended film illuminated in different positions in radial direction. For 1L MoS2 and MoSe2, the room-temperature thermal conductivities are (80±17) W/mK and (55±18) W/mK, respectively. For 2L MoS2 and MoSe2, we obtain values of (73±25) W/mK and (39±13) W/mK. Crucially, the interfacial thermal conductance is found to be of order 0.1-1 MW/m2K, substantially smaller than previously assumed, a finding that has important implications for design and modeling of electronic devices.